1. Field of the Invention
The invention relates to thermoplastically moldable polyester resin compositions.
2. Brief Description of the Prior Art
Polyester resins having properties useful for thermoplastic molding, such as injection molding, are well known. However, not all of the known polyester resins are useful for injection molding. Especially difficult to injection mold are those polyester resins which possess hot-melt adhesive properties. Other polyesters may not be classified as hot-melt adhesives, but when injection molded the heat-softened resin may adhere strongly to metal surfaces after cooling and re-solidifying. One class of such polyester resins are those obtained by the reaction of aromatic dicarboxylic acids with cyclo-aliphatic dialkanols. An example of such polyester resins is the one described in U.S. Pat. No. 2,901,466.
It will be appreciated by those skilled in the art of injection molding that these polyesters are generally unsuited for molding in conventional injection molding apparatus. The polyester wraps itself around the screw and adheres to the metallic surfaces of the injection molding machine.
However, these polyesters have other physical properties which may be desirable in molded articles and in articles molded from blends of adhesive resins with compatible synthetic polymeric resins which are not themselves difficult to mold by thermoplastic molding techniques. We have found that a particular class of mold release agents, added to these polyesters blended with polycarbonates provide thermoplastically moldable compositions which are useful to injection mold a wide variety of articles. The agents do not significantly degrade the molded resin articles, in the proportions employed.